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Discussion Starter #1
Hi again guys!

Seems like I'm gonna be living on these forums now :p

All of a sudden, when I was turning the headlights on (turning the headlight switch to the right), my windscreen wipers come on for quite some time (as if I had pressed the wiperfluid button down.. you know, on the signaling rod.. when you press it down :p, but no wiperfluid comes out though).

It also happens when I turn the signal light on to the right, but not to the left. Happens all the time now, consistantly.

Hmn. I have been working alot on the PSE pump, and before that I had replaced the "exterior lamp failure module", which is kind of next to all the other modules.

Any of you seen this before? Have a clue where to look first? :confused:

Summary: Right turn light = gives a right turn light + windscreen wipers on
Headlights on = gives headlights on + windscreen wipers

There a short somewhere? :p I know electrical problems are the worst to diagnose, but this is so annoying!!
 

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Discussion Starter #2
I know I have been pushing the Wiper Relay out of the way alot because I've had to get to the "exterior lamp failure module", but I can't see any connection to the headlights or turn signal on the wiring diagrams.. except for in the combination switch (the turn signal rod in the steering column).. or the "exterior lamp failure module".

But it happens both with the old "ELF module" unit and the "new" module I bought. So I kind of doubt it's that.

Anyone with spare time can have some fun with these wiring diagrams. Also useful if you need them later:

http://www.autolib.diakom.ru/CAR/Mercedes-Benz/1992/300SE/SYSTEM WIRING DIAGRAMS/
http://s1089.photobucket.com/albums/i360/lacraigslistmechanic/1995 S500 Wiring diagram/
 

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I would say that the fault is on the combination switch, I do not know of much else that would do this
 

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Discussion Starter #4
I would say that the fault is on the combination switch, I do not know of much else that would do this
Alright.. might as well change the combination switch then, so I can at least rule that out. But I have a sneaky suspicion it's not that.

The windscreen wipers also come on when I turn on the hazard lights :p And main headlights.

But then again, maybe there is a short in the combi switch somewhere and it's what's causing it.

Thanks for the reply! :)
 

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Discussion Starter #5
Alright.. might as well change the combination switch then, so I can at least rule that out. But I have a sneaky suspicion it's not that.

The windscreen wipers also come on when I turn on the hazard lights :p And main headlights.

But then again, maybe there is a short in the combi switch somewhere and it's what's causing it.

Thanks for the reply! :)
Just went through all the wiring diagrams for the w140. There must be half a ton of wires in this car!

Noticed that all of the electrical problem areas of the car, are linked by a single relay. The Combination Relay (turn signal relay), N10 in the diagrams. I googled it and it may just be the source of all my problems.

1. My brake lights don't work, even though I've replaced pretty much everything else on the way from the brakepedal (brake light switch, exteriour lamp failure module, light bulbs).
2. The windshield wipers come on if I:
a) turn the headlights on
b) turn the signal lights on to the right
c) turn on the hazard lights
d) and sometimes when I start the car

What do you guys think? This would be a better place to start than buying the combination switch?
 

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The missing link is that the lights do not go through the N10, but the dip/main is in the stalk as are the wipers.

The N10 has the heated rear window,wipers and indicators in it.


I cannot think of any other reason than the stalk,,no one wants you to buy what you do not need,, does anyone else know better on this
 

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Discussion Starter #7
The missing link is that the lights do not go through the N10, but the dip/main is in the stalk as are the wipers.

The N10 has the heated rear window,wipers and indicators in it.


I cannot think of any other reason than the stalk,,no one wants you to buy what you do not need,, does anyone else know better on this
Thanks for your replies Television!

I have now changed the stalk (combination switch in MB terms), and I discovered something interesting. The previous owner had installed xenon lights, and I assume that he has had some problems doing this, as there were some extra wires connected to the wires from the combination switch. I cut those off, put a new combination switch in and.. well, the headlights don't come on automatically anymore, if they are turned on however by the headlight switch, the window wipers come on :(

So, the problem is in the wiring somewhere. Everything else has been replaced. And in the drivers side footwell there is a ton of wiring and alot of it seems like it's not original.

I'm getting an auto electrician to take a look at it. Expensive but it's the only way for me now.

Brake lights still don't work. This car is giving me so much grief :'(
 

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check the earth returns from the lights, brakes, wipers, and especially the xenon headlamps. I suspect that if someone has monkeyed with the wiring there will be a bad earth somewhere. I'd definitely also check the earths on the combination relay that has the wiper, indicator and light relays in it. This is classic "bad earth" stuff

cheers

Dave
 

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You may have a differential potential in ground; The ground "floated"

Measure the ground from the device to the ground terminal of the battery. I would accept no more than 0.5v dc for a low current device such as the wipers .

You will need to make a long voltmeter lead to get to the battery

Check all the ground landings for corrosion

This is the same problem for audio systems with excessive hum...Here you are creating noise in the electrical bus, and upsetting the microprocessor controlled devices...

Best of luck,

Martin
 

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Discussion Starter #11
check the earth returns from the lights, brakes, wipers, and especially the xenon headlamps. I suspect that if someone has monkeyed with the wiring there will be a bad earth somewhere. I'd definitely also check the earths on the combination relay that has the wiper, indicator and light relays in it. This is classic "bad earth" stuff

cheers

Dave
You know, you just might be right. When I hook the antenna up to the radio, there is an alternator whine.. which is also a sign of bad ground. Might be worth the effort to check this myself, I just find the task quite daunting :p

Thanks for the reply! :)
 

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Discussion Starter #12
Found out what the problem was: there was a bad ground at the front passanger side, right behind the headlights. There was so much corrosion that the ground had simply come completely loose from the chassis. I put in a wire, made a new ground connection and voilá: everything works! :D

Thanks you guys, for the help! The car is slowly starting to get back that luxurious feel to it.. first time the cruise control works and it was so sweet :)
 
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